Thomas F. Gesell

Rapid Measurements of 222Rn Concentrations in Water With a Commercial Liquid Scintillation Counter

Abstract A technique is described by which concentrations of 222Rn in water as low as 10 pCi/l can be determined by a 40-min count of a 10-ml sample. Preparation time is about 1 min/sample, and no special equipment is required other than access to a commercial liquid scintillation system.

Background atmospheric 222Rn concentrations outdoors and indoors: a review.

The sources of outdoor and indoor atmospheric radon are examined. The variation of outdoor atmospheric radon with time of day, time of year, altitude and geographic location is quantitatively assessed. Average values of outdoor atmospheric radon concentrations are examined and it is estimated that the mean value for normal areas of the contiguous United States lies in the range of 100-400 pCi/m3 and is probably about 250 pCi/m3. Values for Alaska and Hawaii are an order of magnitude lower. Indoor atmospheric radon concentrations are found to vary with time of day, geographic location and story above ground.

The technologically enhanced natural radiation environment.

Abstract A new category for human radiation exposure, technologically enhanced natural radiation (TENR), is proposed. The purpose of the new category is to permit clear distinction between truly natural human radiation exposure and exposure which occurs due to alteration of the natural sources by non-nuclear technology. Examples of TENR, such as radium emission from coal fired plants, radon in natural gas, radium in fertilizer, radon in water and enhanced cosmic ray exposure in high altitude aircraft are discussed. It is concluded that creation of the TENR category would be useful because (1) it would facilitate direct comparison of increments to the radiation environment due to nuclear and conventional activities, (2) it would direct research to TENR which would perhaps uncover significant human exposure and (3) it would permit regulatory authorities to control unambiguously TENR exposures without having to decide in each instance whether the exposure was natural or man-made.

An estimate of population exposures due to radon in public water supplies in the area of Houston, Texas.

An estimate of the incremental population lung exposures (WLM) attributable to the domestic use of ground waters containing z2zRn is made for the vicinity of Houston, Texas. Because of the complexity of the water distribution system, extensive water sampling was required to characterize the concentration of radon in the water in various areas. Models describing the transfer of radon from water to indoor air and the resulting indoor concentrations were developed and experimentally tested. Census data on population and housing characteristics were folded into the final model used to compute an annual population exposure of 4000 WLM (approx. 40,000 rem) to the 1.6 million inhabitants of the study area. The resulting estimates are discussed in the context of similar exposures brought about by other technological activities.

Residential radon exposure and lung cancer: risk in nonsmokers.

Lung cancer is a disease that is almost entirely caused by smoking; hence, it is almost totally preventable. Yet there are a small percentage of cases, perhaps as many as 5 to 15%, where there are other causes. Risk factors identified for this other group include passive smoking, occupational exposure to certain chemicals and ionizing radiation, diet, and family history of cancer. In the United States cigarette smoking is on the decline among adults, occupational exposures are being reduced, and people are being made more aware of appropriate diets. These changes are gradually resulting in a reduced risk for this disease. Lung cancer in the U.S. may, therefore, eventually become largely a disease of the past. It remains important, however, to continue to study the cause(s) of lung cancer in non-smokers, particularly never smokers. Because of our interest in the effects of residential radon exposure on the development of lung cancer in non-smokers, we conducted a critical review of the scientific literature to evaluate this issue in detail. Strict criteria were utilized in selecting studies, which included being published in a peer reviewed journal, including non-smokers in the studied populations, having at least 100 cases, and being of case-control design. A total of 12 individual studies were found that met the criteria, with 10 providing some information on non-smokers. Most of these studies did not find any significant association between radon and lung cancer in non-smokers. Furthermore, data were not presented in sufficient detail for non-smokers in a number of studies. Based on the most recent findings, there is some evidence that radon may contribute to lung cancer risk in current smokers in high residential radon environments. The situation regarding the risk of lung cancer from radon in non-smokers (ex and never) is unclear, possibly because of both the relatively limited sample size of non-smokers and methodological limitations in most of the individual studies. A summary of these studies is provided concerning the state of knowledge of the lung cancer risk from radon, methodological problems with the residential studies, the need for the provision of additional data on non-smokers from researchers, and recommendations for future research in non-smokers.

Occupational radiation exposure due to 222Rn in natural gas and natural gas products.

Abstract-The potential hazard of occupational exposure to the radiations of 222Rn and its daughters in the natural gas industry is examined. The results ofastudy of222Rn concentrations and external radiation fields in nine geographically diverse natural gas processing plants are given, and the results are interpreted in terms of occupational exposure. It is concluded that while both internal and external exposures to the radiations from 222Rn and its short-lived daughters do occur, the magnitudes of the exposures are not serious. The potential problem of exposure during maintenance operations to long-lived 222Rn daughters which may build up on the interior surfaces of gas processing equipment is recognized but not resolved.

Second international intercomparison of environmental dosimeters.

The second international intercomparison of environmental dosimeters under both field and laboratory conditions was held in New York in 1976. Eighty-five participants from 26 countries submitted 133 sets of 6 dosimeters, primarily TLDs. Upon receipt, the dosimeters were placed in a shielded location (-1.5 pR/hr). At the beginning of the intercomparison period, the field dosimeters were placed in close proximity, about 1 m above the ground, in a field location for 3 months while the laboratory and control dosimeters remained in the shield. Six weeks after the start of the study, the laboratory dosimeters were briefly removed from the shield and given a known but unrevealed gamma radiation exposure. At the end of the 3 months, the dosimeters were returned to the participants, who evaluated them and reported their results. The significant findings included: ( 1 ) Thirty-six and 81% of the laboratory results were within 10 and 30% of the estimated delivered exposure of 21.3 mR, and 32 and 80% of the field results were within 10 and 30% of the average field exposure, 16.4 mR. (2) No significant differences were found among the results for three of the most commonly used phosphors, LiF, CaFz: Dy, and CaS04:Cy. CaF2: Mn, while exhibiting good agreement for the laboratory exposure, yielded an average field exposure 10% lower than the average for all dosimeters. (3) The laboratory results correlated with the calibration sources used by the participants, with the exposure estimates ranging from high to low for calibrations performed with “Co, I3’Cs and 226Ra, respectively. (4) Analysis of the field and laboratory results revealed that the standard deviation of the results obtained by participants calculating their calibration exposures, based on source strength and distance, exceeded that for those actually measuring their calibration exposures by a factor of two. (5) The field results for LiF revealed a significant correlation with packaging thickness, suggesting that phosphors with surrounding material of a thickness less than about 300 mg/cm2 responded to environmental beta radiation as well as gamma radiation. (6) Control dosimeters indicated transit and storage exposures of a few mR up to slightly over 100 mR, with the majority ranging from 1 to 15 mR. The typical transit time was 2 weeks. Future intercomparisons of this type are planned by the authors.

Distribution of 137Cs in soil along Ta-han River Valley in Tau-Yuan County in Taiwan

Environmental 137Cs contamination was suspected from accidents at spent fuel storage pits of a research reactor site in the Ta-han River valley in Taiwan. In order to further characterize this contamination, soil samples were collected and measured by a gamma-spectroscopy system in 1999. It was found that 137Cs contamination is distributed up to 4 km from the reactor in an area covered mostly by rice and plant fields. 137Cs concentration in the topsoil ranged up to about 1000 Bq kg-1, as compared with soil beyond the contaminated area, which does not exceed 15 Bq kg-1. Spatial distribution of 137Cs was characterized by strong non-uniformity, which complicated our understanding of the distribution pathway of the radionuclides. The highest concentrations of 137Cs, up to more than 1000 Bq kg-1, were found within a few rice fields. The relative location of these rice fields and the water supplies from local streams suggested that the 137Cs was distributed along water pathways in the valley.

Highlights of the fourth international intercomparison of environmental dosimeters under field and laboratory conditions

Abstract The Fourth International Intercomparison of Environmental Dosimeters, primarily thermoluminescence dosimeters, was held in Houston, TX in 1979. A description of the study and highlights of the results are presented.

Effect of vitamin A on lung tumorigenesis in irradiated and unirradiated strain A mice

The effect of vitamin A (retinyl acetate) on lung tumor development in strain A mice exposed to radiation was assessed. Four groups of 75 mice were utilized. Two groups were fed a low vitamin A diet (less than 100 IU/100 g diet) and the other 2 were fed a high vitamin A diet (800 IU/100 g diet). After 2 weeks one group maintained on the high vitamin A diet and one group maintained on the low vitamin A diet were given an acute dose of 500 rad of gamma radiation to the thoracic region. Circulating levels of plasma vitamin A in all 4 groups of mice were monitored. A difference in circulating vitamin A in the mice maintained on high and low vitamin A diet became evident by 20 weeks and continued for the duration of the experiment. Mice were killed 18, 26 and 40 weeks post-irradiation, their lungs were removed and the number of surface adenomas were counted. There was a significant increase in the number of mice bearing lung tumors and the mean number of lung tumors per mouse in the irradiated group maintained on the high vitamin A diet at 40 weeks post-irradiation as compared to the irradiated group maintained on a low vitamin A diet. Under the conditions of this experiment the development of pulmonary adenomas in irradiated strain A mice appears to relate directly to circulating levels of vitamin A.